Achotegui-Castells A., Llusia J., Hodar J.A., Penuelas J. (2013) Needle terpene concentrations and emissions of two coexisting subspecies of Scots pine attacked by the pine processionary moth (Thaumetopoea pityocampa). Acta Physiologiae Plantarum. 35: 3047-3058.EnllaçDoi: 10.1007/s11738-013-1337-3
Mediterranean pine forests are often attacked by caterpillars of Thaumetopoea pityocampa (Lep., Thaumetopoidae), one of the most important defoliators in the Mediterranean region causing large economic losses and ecological effects. The needle terpene concentrations and emissions may play a key role in the defense of pines. We studied two subspecies of Pinus sylvestris, nevadensis (an endemic and relict subspecies) and iberica, with different levels of caterpillar attack in Sierra Nevada mountains (Spain). GC-MS analyses showed large total concentrations of terpenes (6 to 39 mg g-1 of dry weight) in the needles of both subspecies under field conditions. Concentrations were 25 % higher in "Non-Attacked Trees" (NATs) of the iberica than in the nevadensis subspecies. The branches of NATs had terpene concentrations 20 % higher than those of "Attacked Branches of attacked trees" (ABs). Within attacked trees, the "Non-Attacked Branches" (NABs) also had terpene concentrations 20 % higher than those of ABs. Mainly α-pinene and germacrene D had higher concentrations in NATs and NABs than in ABs. Some terpenes had higher concentrations in NABs than in NATs, indicating possible systemic reactions. In subsp. nevadensis, the percentage of monoterpenes relative to total terpenes was higher in ABs than in other attack states. The rates of emission in nevadensis (standardized to 30 °C) were ca. three times higher in ABs than in NABs and NATs. These results suggest that the lower terpene concentrations and high percentages of monoterpenes in ABs were produced by a combination of emission losses and terpene induction in response to herbivorous attack. © 2013 Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Kraków.
Achotegui-Castells A., Sardans J., Ribas À., Peñuelas J. (2013) Identifying the origin of atmospheric inputs of trace elements in the Prades Mountains (Catalonia) with bryophytes, lichens, and soil monitoring. Environmental Monitoring and Assessment. 185: 615-629.EnllaçDoi: 10.1007/s10661-012-2579-z
The biomonitors Hypnum cupressiforme and Xanthoria parietina were used to assess the deposition of trace elements and their possible origin in the Prades Mountains, a protected Mediterranean forest area of NE Spain with several pollution sources nearby. Al, As, Cd, Co, Cu, Cr, Ni, Pb, Sb, Ti, V, and Zn were determined in 16 locations within this protected area. Soil trace element concentrations were also ascertained to calculate enrichment factors (EF) and use them to distinguish airborne from soilborne trace element inputs. In addition, lichen richness was measured to further assess atmospheric pollution. EF demonstrated to be useful not only for the moss but also for the lichen. Cd, Cr, Cu, Ni, and Zn presented values higher than three in both biomonitors. These trace elements were also the main ones emitted by the potential sources of pollutants. The distance between sampling locations and potential pollution sources was correlated with the concentrations of Cu, Sb, and Zn in the moss and with Cr, Ni, and Sb in the lichen. Lichen richness was negatively correlated with lichen Cu, Pb, and V concentrations on dry weight basis. The study reflected the remarkable influence that the pollution sources have on the presence of trace elements and on lichen species community composition in this natural area. The study highlights the value of combining the use of biomonitors, enrichment factors, and lichen diversity for pollution assessment to reach a better overview of both trace elements' impact and the localization of their sources. © 2012 Springer Science+Business Media B.V.
Ameztegui A., Coll L. (2013) Unraveling the role of light and biotic interactions on seedling performance of four Pyrenean species along environmental gradients. Forest Ecology and Management. 303: 25-34.EnllaçDoi: 10.1016/j.foreco.2013.04.011
The predicted upward displacement of forest species due to climate warming is expected to be modulated by a medley of abiotic and biotic factors acting at microsite level. Species-specific differences in plant responses to this set of environmental factors can thus have strong implications in the future dynamics of forest ecosystems. To gain a better understanding of the main fine-scale factors and processes driving present and future species performance in the montane and subalpine belt of the Eastern Pyrenees (NE Spain), we established a set of experimental mixed plantations along elevational and environmental gradients using the four tree species dominating these areas (Pinus sylvestris, Pinus uncinata, Abies alba and Betula pendula). Once the plantations had been established, the performance and growth of 72 seedlings of each species was monitored and linear and non-linear models were fitted to identify the main factors controlling their survival and growth.We found most of the mortality to occur during the third growing season, following a harsh winter and a drought period during summer. Mortality patterns were highly species- and site-specific. At the subalpine belt, shrubs were found to have a facilitative effect on winter survival of P. sylvestris (mortality. <. but="" not="" on="" the="" other="" species.="" at="" montane="" belt="" a.="" alba="" mortality="" during="" summer="" increased="" in="" areas="" with="" high="" light="" exposure="" and="" herbaceous="" cover="">30%). All species except P. uncinata showed lower height growth at high elevation, with differences between sites matching differences in growing season duration (20%).Our results underline the strong impact that short periods of extreme climate can have in the performance of plants developing in mountainous areas far from their optimal elevational range. However, they also underline a potentially critical role played by biotic and abiotic microsite factors in mediating species responses to these climatic events. © 2013 Elsevier B.V..
Andersen A.N., Arnan X., Sparks K. (2013) Limited niche differentiation within remarkable co-occurrences of congeneric species: Monomorium ants in the Australian seasonal tropics. Austral Ecology. 38: 557-567.EnllaçDoi: 10.1111/aec.12000
Niche theory predicts that few closely related species can co-occur because such species tend to be ecologically similar and niche differentiation is required to avoid competitive exclusion. We analyse the co-occurrence of a remarkable 10-15 species of the ant genus Monomorium occurring within single 10×10m plots in a tropical savanna of northern Australia. Most of the species are undescribed, so we use genetic analysis to validate our species demarcations. We document nest dispersion patterns, and investigate differentiation in the three primary niche dimensions: space, time and food. We also examine species differences in competitive abilities, by describing rates of foraging activity, foraging ranges, worker aggression, and levels of behavioural dominance. Analyses of nest and forager distributions showed very limited evidence of spatial segregation within plots. The great majority of species foraged either exclusively or primarily during daylight hours. Body size and isotopic analyses indicated very limited dietary differentiation. Such limited niche partitioning occurred despite the species differing markedly in their competitive abilities as measured by rates of resource discovery, recruitment and monopolization. Our findings defy the traditional assumption that multiple closely related and ecologically similar species of highly interactive taxa cannot co-occur. It seems very likely that species coexistence in our study system is determined to a very large degree by stochastic processes relating to dispersal and establishment, as predicted by neutral theory. However, neutral theory assumes competitive equivalence, whereas we found very marked differences in the competitive abilities of our co-occurring species. We suggest that competitive exclusion is prevented by the modular nature of ant colonies, with competition limiting colony performance but not preventing occurrence. We conclude that other factors that allow species persistence, and not just competitive equivalence, can allow dispersal and establishment processes to drive species coexistence. © 2012 Ecological Society of Australia.
Armenteras D., Cabrera E., Rodríguez N., Retana J. (2013) National and regional determinants of tropical deforestation in Colombia. Regional Environmental Change. 13: 1181-1193.EnllaçDoi: 10.1007/s10113-013-0433-7
Global tropical deforestation continues to occur at high rates despite political attention. National-level forest baselines are being established all over the world to guide the implementation of several policy mechanisms. However, identifying the direct and indirect drivers of deforestation and understanding the complexity of their interlinkages are often difficult. We first analyzed deforestation between 1990 and 2005 at the national level and found an annual deforestation rate of 0.62 %. Next, we performed separate analyses for four natural regions in Colombia and found annual deforestation rates between 0.42 and 1.92 %. Using general linear models, we identified several direct causes and underlying factors influencing deforestation at the national level: rural population density, cattle, protected areas, and slope. Significant differences in deforestation rates and causes were found across regions. In the Caribbean region, drivers of loss are urban population, unsatisfied basic needs, slope, and precipitation and four land use variables (illicit crops, pastures, cattle, and fires). In the Orinoco region, crops are the main driver of forest loss, and in the Amazonian region, deforestation is primarily due to fires related to the colonization front. Policy mechanisms will have to take into account regional patterns to successfully balance development and forest preservation in Colombia. © 2013 Springer-Verlag Berlin Heidelberg.
Armenteras D., González T.M., Retana J. (2013) Forest fragmentation and edge influence on fire occurrence and intensity under different management types in Amazon forests. Biological Conservation. 159: 73-79.EnllaçDoi: 10.1016/j.biocon.2012.10.026
The ecological characteristics of forest edges have been intensively studied in the Amazon region, but the occurrence and intensity of fires as large-scale edge effects are less well known, as is the role of different types of management in modifying this relationship. We used remote sensing techniques to examine the relationship between forest fragmentation, fire and management across NW Amazonia. Our study was based on forest data for 2005 and on active fire data from the MODerate-resolution imaging Spectro-radiometer (MODIS), with information on the occurrence and strength of fires based on fire radiative power (FRP) data. We analyzed the fragmentation and fire occurrence and intensity in a 50 × 50. km grid. We also calculated the distance at which edge-related fires occur in the forest interior and outside the forest edge. Forest fragmentation had a significant impact on fire occurrence and fire intensity, supporting the hypothesis that the more fragmented a forest is, the higher the degree of biomass combustion. These results are in agreement with the occurrence of an edge effect on both the occurrence and the intensity of fire. The different types of management in the region influence the occurrence and intensity of fire, whereas fire as a large-scale edge effect occurs independent of the management type. Finally, we suggest that a high connectivity in protected areas and indigenous reserves and also in outside areas should be encouraged to minimize edge-driven fire processes. © 2012 Elsevier Ltd.
Arnan X., Cerda X., Rodrigo A., Retana J. (2013) Response of ant functional composition to fire. Ecography. 36: 1182-1192.EnllaçDoi: 10.1111/j.1600-0587.2013.00155.x
Little is known about the impact of disturbances on functional diversity and the long-term provisioning of ecosystem services, especially in animals. In this work we analyze the effect of wildfire on the functional composition of Mediterranean ant communities. In particular, we asked whether a) fire changes functional composition (mean and dissimilarity of trait values) at the community level; and b) such fire-induced functional modification is driven by changes in the relative abundance-dominance of species or by a replacement of species with different traits. We sampled ant communities in burned and unburned plots along 22 sites in a western Mediterranean region, and we computed two complementary functional trait composition indices ('trait average' and 'trait dissimilarity') for 12 functional traits (related to resource exploitation, social structure and reproduction) and with two different datasets varying in the way species abundance is considered (i.e. abundance and occurrence data). Our results suggest a set of functional responses that seem to be related to direct mortality by fire as well as to indirect fire-induced modifications in environmental conditions relevant for ants. Trait average of colony size, worker size, worker polymorphism and the ratio between queen and worker size, as well as the trait dissimilarity of the proportion of behaviorally dominant species and of liquid food consumption, and overall functional diversity, were higher in burned than in unburned areas. Interestingly, different patterns arise when comparing results from abundance and occurrence data. While the response to fire in trait averages is quite similar, in the case of trait dissimilarity, the higher values in response to fire are much more marked when considering occurrence rather than abundance data. Our results suggest that changes in trait average are driven at the same time by replacement of species with different traits and by changes in the relative abundance-dominance of species, while fire promotes a higher diversity of functions that is primarily driven by rare species that are functionally unique. Overall, we observed major fire-induced changes in functional composition in Mediterranean ant communities that might have relevant consequences for ecosystem processes and services. © 2013 The Authors.
Arnan X., Quevedo L., Rodrigo A. (2013) Forest fire occurrence increases the distribution of a scarce forest type in the Mediterranean Basin. Acta Oecologica. 46: 39-47.EnllaçDoi: 10.1016/j.actao.2012.10.005
Here we report how fire recurrence increases the distribution of a scarce forest type in NE Spain that is dominated by the resprouter tree species Arbutus unedo. We used a combination of GIS and field surveys to determine the effect of fire and pre-fire vegetation on the appearance of A. unedo forests. In the field, we also analyzed the factors that promote fire and lead to the appearance of A. unedo forests. Our results reveal an increased occurrence of A. unedo forests in NE Spain in recent years; this phenomenon was strongly related to fire recurrence and the vegetation type present prior to fire. Most Pinus halepensis forests that burned more than once gave rise to A. unedo forests. Our results indicate that these conversions were related to a reduction in pine density coupled with increases in the density and size of A. unedo trees due to recurrent fires. Given that fires are increasing in number and magnitude in the Mediterranean, we predict a major change in landscape structure and composition at the regional scale. © 2012 Elsevier Masson SAS.
Atherton, J.M., Nichol, C.J., Simpson, K. (2013) The utility of optical remote sensing for characterizing changes in the photosynthetic efficiency of Norway maple saplings following transplantation. International Journal of Remote Sensing. 34: 655-667.EnllaçDoi: 10.1080/01431161.2012.715778
Ba M.N., Baoua I.B., N'Diaye M., Dabire-Binso C., Sanon A., Tamo M. (2013) Biological control of the millet head miner Heliocheilus albipunctella in the Sahelian region by augmentative releases of the parasitoid wasp Habrobracon hebetor: Effectiveness and farmers' perceptions. Phytoparasitica. 41: 569-576.EnllaçDoi: 10.1007/s12600-013-0317-x
On-farm augmentative releases of the parasitoid Habrobracon hebetor (Say) for controlling the millet head miner (MHM) Heliocheilus albipunctella (de Joannis) were tested in Burkina Faso, Mali and Niger from 2007 to 2009. In addition, a survey of farmers' perceptions of insect pests, with particular focus on MHM, and the biological control program (BCP) was carried out. There was a significant increase of MHM parasitization rate after the releases, with up to 97% mortality. The survey on farmers' perceptions revealed a fair knowledge of the MHM and the ability of farmers to describe the pest and the damage it caused. Farmers claimed that the biocontrol agent H. hebetor is effective and perceived a significant gain in grain yield due to this control strategy. Implications of these findings for a large extension of the MHM biocontrol program are discussed. © 2013 Springer Science+Business Media Dordrecht.
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